use Data::Dumper;
use strict;

my $h1 = {"a" => 1, "b" => 2};
my $h2 = {"c" => 1, "b" => 3};
my $ret = plus($h1, $h2);
print Dumper($ret);

sub plus {
	my $ret = {};
	my ($hash1, $hash2) = @_;
	for (keys %$hash1) {
		if (exists($hash2->{$_})) {
			$ret->{$_} = $hash1->{$_} + $hash2->{$_};
		} else {
			$ret->{$_} = $hash1->{$_};
		}
	}	
	return $ret;
}